1. Field of the Invention
This invention relates to lubricant compositions and more particularly to water-soluble lubricant compositions adapted for use as lubricants and coolants in metal machining operations.
2. Description of the Prior Art
In the machining of metals (turning and drilling etc.) it is often necessary to have a liquid flowing over the contact of workpiece and tool, in order to provide cooling and lubrication and to wash away the chips. The fluids used are of two general types, soluble cutting oils and straight cutting oils. In some cutting operations, such as turning and grinding, cooling is more important than lubrication. Water is the best coolant known, and at one time water or an aqueous soap solution was used for this purpose. Such liquids possess poor lubricating properties, however, and moreover lead to rusting when used with ferrous metals. Consequently, `soluble` oils were developed for this kind of operation. They consist of mixtures of mineral oils and emulsifiers which can be diluted with water to form stable emulsions over a wide range of concentrations and possess the good cooling properties of water, while containing sufficient oil to provide lubrication. They are normally used as dilute emulsions, which circulate over the seat of the cutting operation and, besides cooling and lubricating, carry away the metal particles formed. A number of emulsifiers can be used, but one of the best types is a petroleum soap (i.e. sodium naphtha-sulphonates), made from the aromatics produced in the refining of medicinal oils, transformer oils and white oils. More recently there has been a tendency to return to improved forms of aqueous solutions free from some of the deficiencies of their earlier counterparts.
It is customary to employ these coolants in combination with various agents having lubricating and extreme-pressure properties for reducing friction between the tool and workpiece, particularly in operations such as tapping and broaching. Such aqueous cutting fluids, in order to perform satisfactorily, should meet certain important requirements.
Among the requirements for a satisfactory aqueous cutting fluid are corrosion-inhibiting properties for ferrous and cuprous alloys, and also stability under the conditions of operation. There are, however, further important requirements that should also be met. Among these requirements is the ability to avoid leaving deposits on the tool and the work following the machining operation which result from subsequent drying of the fluid and which are difficult to remove. Other important requirements include tolerance in hard water solutions so that the precipitation of lubricant components will not occur, avoidance of tacky residues which interfere with the operation of the machine and avoidance of excessive foam formation. Aqueous metal working fluids known prior to this invention have not, however, proven satisfactory for all of the foregoing requirements.
U.S. Pat. No. 3,723,313 teaches lubricants for metal working that contain an aromatic oil and a mixture of mono- and dialkyl phosphates, the alkyl groups having 8 to 20 carbon atoms. U.S. Pat. No. 3,523,895 teaches an emulsion lubricant on a water-free basis from about 20-50% by weight of the neat composition of a solid aliphatic monocarboxylic acid having from 10 to 30 carbon atoms. There are, however, no such aqueous systems incorporating amides derived from amines as disclosed and claimed in accordance herein.